Mechanism of lead immobilization by oxalic acid-activated phosphate rocks

Lead （Pb） chemical fixation is an important environmental aspect for human health. Phosphate rocks （PRs） were utilized as an adsorbent to remove Pb from aqueous solution. Raw PRs and oxalic acid-activated PRs （APRs） were used to investigate the effect of chemical modification on the Pb-binding capacity in the pH range 2.0-5.0. The Pb adsorption rate of all treatments above pH 3.0 reached 90%. The Pb binding on PRs and APRs was pH-independent, except at pH 2.0 in activated treatments. The X-ray diffraction analysis confirmed that the raw PRs formed cerussite after reacting with the Pb solution, whereas the APRs formed pyromorphite. The Fourier Transform Infrared spectroscopy analysis indicated that carbonate （CO32-） in raw PRs and phosphate （PO43-） groups in APRs played an important role in the Pb-binding process. After adsorption, anomalous block-shaped particles were observed by scanning electron microscopy with energy dispersive spectroscopy. The X-ray photoelectron spectroscopy data further indicated that both chemical and physical reactions occurred during the adsorption process according to the binding energy. Because of lower solubility of pyromorphite compared to cerussite, the APRs are more effective in immobilizing Pb than that of PRs.

Immobilization of lead in anthropogenic contaminated soils using phosphates with/without oxalic acid

Understanding the effects of oxalic acid（OA） on the immobilization of Pb（Ⅱ） in contaminated soils by phosphate materials, has considerable benefits for risk assessment and remediation strategies for the soil. A series of phosphate amendments with/without oxalic acid were applied to two anthropogenic contaminated soils. We investigated the immobilization of Pb（Ⅱ） by KH2PO4, phosphate rock（PR）, activated phosphate rock（APR） and synthetic hydroxyapatite（HAP） at different phosphate：Pb（P：Pb） molar ratios（0, 0.6, 2.0 and 4.0） in the presence/absence of 50 mmol oxalic acid/kg soil, respectively. The effects of treatments were evaluated using single extraction with deionized water or Ca Cl2, Community Bureau of Reference（BCR） sequential extraction and toxicity characteristic leaching procedure（TCLP）methods. Our results showed that the concentration of water extractable, exchangeable and TCLP-Pb all decreased with incubation time. The concentration of water-extractable Pb after120 days was reduced by 100% when soils were amended with APR, HAP and HAP ＋ OA, and the TCLP-Pb was 〈5 mg/L for the red soil at P：Pb molar ratio 4.0. Water-soluble Pb could not be detected and the TCLP-Pb was 〈5 mg/L at all treatments applied to the yellow-brown soil. BCR results indicated that APR was most effective, although a slight enhancement of water-soluble phosphate was detected at the P：Pb molar ratio 4.0 at the beginning of incubation. Oxalic acid activated phosphates, and so mixing insoluble phosphates with oxalic acid may be a useful strategy to improve their effectiveness in reducing Pb bioavailability.

Efficiency of KOH-modified rice straw-derived biochar for reducing cadmium mobility, bioaccessibility and bioavailability risk index in red soil

Cadmium(Cd)pollution in agricultural soils has exerted a serious threat due to continuous application of pesticides,fertilizers,and wastewater irrigation.The present study aimed to test the efficiency of KOH-modified and non-modified rice straw-derived biochar(KBC and BC,respectively)for reducing Cd solubility and bioavailability in Cd-contaminated soil.Cadmium-contaminated soil was incubated for 60 d with 15 and 30 g kg-1 BC and KBC.At the end of incubation,Cd mobility was estimated by the European Community Bureau of Reference sequential extraction and toxicity characteristic leaching procedure(TCLP),while bioavailability was determined using 1 molL-1 NH4NO3 extraction.The bioavailability risk index and bioaccessibility,assessed by a simple bioaccessibility extraction test,of Cd were used to examine the potential effects of Cd on living organisms.The results indicated that application of both KBC and BC significantly increased soil p H,cation exchange capacity,nutrients,and organic carbon.The soluble fraction of Cd was significantly decreased by 30.3%and 27.4%,respectively,with the addition of KBC and BC at 30 g kg-1 compared to the control(without biochar addition).Similarly,the bioaccessible Cd was significantly decreased by 32.4%and 25.2%,respectively,with the addition of KBC and BC at 30 g kg-1 compared to the control.In addition,both KBC and BC significantly reduced Cd leaching in the TCLP and NH4NO3-extractable Cd in the amended soil compared to the control.The reduction in Cd solubility and bioaccessibility by KBC and BC may be due to significant increases in soil pH and surface complexation.Overall,KBC at an application rate of 30 g kg-1 demonstrated positive results as soil amendment for Cd immobilization,and reduced bioaccessible Cd in contaminated soil.

Transcriptome analysis reveals therapeutic potential of NAMPT in protecting against abdominal aortic aneurysm in human and mouse

Abdominal Aortic Aneurysm(AAA)is a life-threatening vascular disease characterized by the weakening and ballooning of the abdominal aorta,which has no effective therapeutic approaches due to unclear molecular mechanisms.Using single-cell RNA sequencing,we analyzed the molecular profile of individual cells within control and AAA abdominal aortas.We found cellular heterogeneity,with increased plasmacytoid dendritic cells and reduced endothelial cells and vascular smooth muscle cells(VSMCs)in AAA.Up-regulated genes in AAA were associated with muscle tissue development and apoptosis.Genes controlling VSMCs aberrant switch from contractile to synthetic phenotype were significantly enriched in AAA.Additionally,VSMCs in AAA exhibited cell senescence and impaired oxidative phosphorylation.Similar observations were made in a mouse model of AAA induced by Angiotensin II,further affirming the relevance of our findings to human AAA.The concurrence of gene expression changes between human and mouse highlighted the impairment of oxidative phosphorylation as a potential target for intervention.Nicotinamide phosphoribosyltransferase(NAMPT,also named VISFATIN)signaling emerged as a signature event in AAA.NAMPT was significantly downregulated in AAA.NAMPT-extracellular vesicles(EVs)derived from mesenchymal stem cells restored NAMPT levels,and offered protection against AAA.Furthermore,NAMPT-EVs not only repressed injuries,such as cell senescence and DNA damage,but also rescued impairments of oxidative phosphorylation in both mouse and human AAA models,suggesting NAMPT supplementation as a potential therapeutic approach for AAA treatment.These findings shed light on the cellular heterogeneity and injuries in AAA,and offered promising therapeutic intervention for AAA treatment.